# Bonding Raceway, GFCI Nuisance Tripping and More

If you have a problem related to the National Electrical Code (NEC), are experiencing difficulty in understanding a Code requirement, or are wondering why or if such a requirement exists, ask Charlie, and he will let the Code decide. Questions can be sent to codefaqs@earthlink.net. Answers are based on the 2011 NEC.

Bonding both ends of a raceway
A recent job required me to bond both ends of a raceway to the grounding-electrode conductor. The raceway was enclosing the grounding--electrode conductor. What is the purpose of this requirement?
If a ferrous (iron) metal raceway is used to enclose the grounding-electrode conductor, the grounding-electrode conductor must be bonded to the raceway at both ends [250.64(E)] to ensure the raceway and the conductor are in parallel. This is to prevent an inductive choke on the grounding-electrode conductor. When current is flowing in the grounding--electrode conductor, the condition creates a magnetic field around that conductor. The build up and collapse of this magnetic field with the alternating-current flow induces a current flow in the raceway. This current flow is in an opposite direction and opposes or chokes the current flow on the grounding--electrode conductor. Paralleling the raceway and the grounding-electrode conductor prevents this choke effect.

Concrete-encased electrodes vs. grounding rods
Why do the people who make the NEC believe the “concrete-encased electrode” is better than the two ground rods in “direct” contact with the ground?
Extensive testing has shown that ground rods deteriorate over time, and their effectiveness is reduced considerably. Concrete-encased electrodes have greater contact with the earth and will be there as long as the building is there.

The cause of GFCI nuisance tripping
What causes nuisance tripping of ground-fault circuit interrupters (GFCIs)?
A GFCI will open when it senses a current flow to ground of 4 to 6 milliamps (mA). If it opens without 4 to 6 mA flowing to ground, it is defective. If the installer follows the manufacturer’s instructions [110.3(B)], there should be no tripping, nuisance or otherwise, unless there is a ground fault.

Code oversight with regard to enclosure location
Why do enclosures in wet locations above ground not have the same clear statement as shown in 300.5(B) for underground installations? Have I missed something, or can terminations in above-ground enclosures installed in a wet location be other than ones listed for a wet location? It seems to me that, if I run my raceways with the fittings to make them “raintight “ (225.22) and the inside of the raceway is still considered a wet location, the same thought should apply to enclosures installed with the same integrity.
The accepted proposal for considering the interiors of raceways—installed in wet locations above ground—as wet locations did not include enclosures (as 300.5(B) shows for underground locations). However, the absence of the requirement to include enclosures installed above ground outdoors does not mean the enclosures are considered a dry location. The conductors installed in outdoor raceways above grade must be listed as suitable for use in a wet location [310.10(C)(3)]. The enclosures are subject to the same condensation effects as the raceway. I thought this oversight would be corrected in the 2011 NEC, but we’ll have to wait for the 2014 Code.

Moisture inside and outside raceways
Can you explain “arranged to drain” in 225.22 and 230.52? Is this in reference to moisture inside or outside of the raceway?
This requirement covers the moisture that accumulates within the raceway due to condensation caused by the temperature difference between the air inside and surrounding the raceway. Properly installed raceways on the exterior of a building will prevent the entrance of water from rainfall. Raceways installed on the exterior of a building can be arranged to drain by providing weep holes at low points in the run and in junction boxes.

Tamper-resistant receptacles
I am curious about your response in the January issue about tamper-proof receptacle requirements. It would seem that the building (a woodworking workshop) could have receptacles that are not dedicated to machinery and could be considered convenience outlets. NEC 210.52(G)(1) provides a requirement for receptacle outlets in addition to those for specific equipment. Would not such convenience receptacles be required to be tamper-proof?
Upon further review, I believe you are correct. At least one receptacle outlet is required by 210.52(G)(1) in the accessory building and must be tamper-resistant in accordance with 406.12. However, note that “tamper-proof” is not the terminology used; the correct term is “tamper-resistant.”

Ground-fault protection minimum
I am installing a 1,200-amp (A) I-line panel as a service entrance with four breakers: 600A, 400A, 250A and 225A. NEC 230.71 allows me to do this without a main disconnect. However, my customer and I would prefer to install a 1,200A main breaker in this panel so that only one handle pull would be required to disconnect the service. According to 230.95, I need ground-fault protection on a service disconnect of 1,000A or larger. My understanding is that the four breakers used by themselves as the service-disconnecting means would not require ground-fault protection under 230.95. Are we required to have ground-fault protection on a main breaker installed in this same panel as long as there are six or less individual breakers all under 1,000A?
Ground-fault protection of equipment is required only for service disconnects rated 1,000A or more on grounded wye services of more than 150 volts to ground (230.95). If you install a 1,200A main disconnect on a grounded wye service, it falls under this requirement, and ground-fault protection of equipment is required.

Bath fan/light and ground-fault protection
If an approved bath fan/light is installed directly above a bathtub or in a shower stall, where in the Code does it state that the circuit supplying it has to be ground-fault-protected?
There is no requirement that a bath fan/light be ground-fault-protected. However, it can be installed on the ground-fault protected 20A branch circuit required by 210.11(C)(3) where it is a single bathroom and the exception is used. The exception refers to 210.23(A)(1) and (A)(2).

Hot tub wiring in dry locations
In regards to using Type NM cable for a hot tub in a dwelling unit, does the Code permit the use of NM cable in dry locations for hot tub wiring?
NEC 680.21(A)(4) permits Type NM cable to be used for hot tub wiring in the interior of dwelling units. Where run in a cable assembly, the equipment--grounding conductor can be uninsulated, but it shall be enclosed within the outer sheath of the cable assembly.